Flexor tendon reconstruction

1. High-Yield Summary

• Primary Clinical Indication: Secondary reconstruction of neglected, lacerated, severely scarred, or failed primary flexor digitorum profundus (FDP) injuries in Zones I through V where myotendinous retraction greater than 4 to 6 weeks, irreversible muscle belly contracture, or dense fibro-osseous sheath obliteration pre-empts direct primary tenorrhaphy.
• The Essential Prerequisite: Full or near-normal passive joint motion must be achieved prior to surgical reconstruction. A tendon graft cannot overcome joint capsular contractures or collateral ligament shortening; attempting reconstruction in a stiff digit uniformly precipitates dense adhesion recurrence and reconstructive failure.
• Single-Stage vs. Two-Stage Paradigm: Single-stage free autografting is strictly restricted to pristine, unscarred synovial beds with intact A2 and A4 pulleys (Boyes Grade I). Severely scarred beds, pulley deficiencies, or failed prior repairs (Boyes Grade II through V) mandate a two-stage Hunter procedure utilizing a passive silicone spacer rod to induce a vascularized, low-friction pseudosheath prior to delayed autografting.
• Pulley Integrity Imperative: The biomechanical continuity of the A2 and A4 annular pulleys must be preserved or anatomically reconstructed using extensor retinaculum or donor tendon slips. Incompetence of these primary restraints generates severe flexor tendon bowstringing, increasing the excursion required for flexion while precipitating dramatic angular motion loss.
• Critical Technical Move: Digital cascade tensioning in 20 to 30 degrees of wrist extension, setting the reconstructed digit in 5 to 10 degrees greater flexion than the adjacent normal digits in the resting cascade. Dynamic intraoperative tenodesis verification must demonstrate complete digital flexion upon wrist extension and unobstructed digital extension upon wrist flexion.

2. Indications

Flexor tendon reconstruction is a demanding secondary salvage procedure indicated when direct primary repair of the flexor digitorum profundus (FDP) or flexor digitorum superficialis (FDS) is precluded by chronicity, proximal tendon retraction, tissue loss, or destructive peritendinous scarring. Surgical decision-making hinges on the Boyes grading system, evaluating the quality of the flexor bed, passive joint mobility, pulley competence, and the regional neurovascular status.

Absolute Indications

• Chronic flexor tendon lacerations or avulsions (greater than 4 to 6 weeks from injury) where proximal muscle belly retraction, interstitial fibrosis, and loss of excursion prevent direct end-to-end advancement without excessive resting tension.
• Segmental tendon loss resulting from high-energy open trauma, industrial crush injuries, blast injuries, deep burns, or extensive localized necrotizing tenosynovitis.
• Failed primary flexor tendon repair complicated by dense peritendinous adhesions unresponsive to comprehensive hand therapy, failed tenolysis, or secondary tendon rupture with sheath obliteration.
• Documented presence of supple passive digital range of motion, with total passive motion (TPM) exceeding 180 degrees across the proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints.

Relative Indications

• Isolated chronic FDP laceration or rupture with an intact, functional FDS tendon (Zone I or Zone II) in high-demand manual laborers, athletes, or musicians who require active DIP joint flexion for power pinch and fine dexterity. In lower-demand patients, DIP joint capsulodesis, tenodesis, or primary arthrodesis is frequently favored to avoid endangering a functional FDS tendon.
• Severely scarred flexor tendon beds with concurrent annular pulley loss (Boyes Grade II to V), where staged silicone spacer reconstruction provides a predictable pathway to functional digital preservation as an alternative to primary ray amputation or joint fusion.

Contraindications

• Active Infection: Persistent soft-tissue infection, unresolved osteomyelitis, or unhealed open contaminated wounds in the operative field.
• Fixed Joint Stiffness: Uncorrected flexion or extension contractures of the PIP or DIP joints, collateral ligament scarring, or severe articular chondral destruction. A tendon graft cannot move a stiff joint.
• Compromised Soft-Tissue Envelope: Unstable, contracted, thin, or ischemic skin coverage over the flexor sheath incapable of sustaining operative exposure without wound breakdown. Reconstruction must be deferred until adequate soft-tissue coverage (e.g., local or microvascular flap) is secured.
• Anesthetic Digit: Complete, non-reconstructible bilateral digital nerve disruption with permanent loss of protective tactile sensation. Reconstruction in an insensate digit yields poor functional utility and high rates of trophic ulceration.
• Unstable Skeletal Framework: Ununited fractures, malunions, or severe skeletal instability of the proximal or middle phalanx.
• Patient Non-Compliance: Cognitive, psychological, or social barriers that preclude strict compliance with an intensive, demanding, multi-month postoperative rehabilitation protocol.

3. Preoperative Planning

Preoperative preparation dictates the success of secondary flexor tendon reconstruction. Complete anatomical mapping of the surviving tendon stumps, pulley integrity, joint mechanics, and autograft donor options must be finalized before entering the operating suite.

Imaging Review

• Plain Radiographs: Standard posteroanterior (PA), lateral, and oblique views of the hand and involved digit. Critical parameters include assessing for prior phalangeal fractures, cortical irregularities within the fibro-osseous canal, joint space narrowing, heterotopic ossification, or retained radiopaque foreign bodies. A true lateral radiograph of the digit confirms absence of fixed joint subluxation or hyperextension deformities.
• Dynamic High-Frequency Ultrasound: Employs 15 to 22 MHz linear transducers to dynamically interrogate the flexor canal. Ultrasound maps the exact anatomical location of the proximal retracted tendon stump (Zone II, Zone III palm, or carpal tunnel), measures stump-to-insertion gap distances, evaluates the cross-sectional integrity of the A2 and A4 pulleys, and assesses the amplitude of passive tendon glide during gentle joint manipulation.
• Magnetic Resonance Imaging (MRI): Dedicated high-resolution 3T MRI using small surface coils provides definitive multiplanar evaluation of the deep flexor apparatus. T1-weighted sequences quantify fatty infiltration and interstitial fibrosis within the proximal FDP muscle belly in the proximal forearm, while T2-weighted and proton density fat-suppressed (PDFS) sequences evaluate fluid-filled fibrous pseudocysts, tenosynovial proliferation, and sheath cicatrization.

Equipment Checklist

• Hunter Passive Tendon Spacer Rods: Sterile silicone Dacron-reinforced flexible rods in graduated outer diameters (3.0 mm, 4.0 mm, and 5.0 mm), accompanied by matching silicone sizing trials.
• Graft Harvesting Instruments: Brand plantaris tendon strippers (closed ring and slotted configurations), palmaris longus tendon strippers, and flexible metallic tendon passers (e.g., Carroll tendon passer, alligator tendon forceps).
• Soft-Tissue & Microvascular Dissection: Stevens tenotomy scissors, Jameson fine curved scissors, micro-Adson toothed forceps, Bishop-Harmon forceps, bipolar micro-forceps, and fine skin hooks.
• Distal Fixation Systems: Micro suture anchors (1.3 mm to 1.8 mm titanium or PEEK anchors preloaded with ultra-high molecular weight polyethylene braided sutures) and pull-out transosseous fixation sets (double-armed straight Keith needles, 3-0 polypropylene suture, sterile convex pull-out buttons, and felt bolsters).
• Anastomosis Sutures: 2-0, 3-0, and 4-0 non-absorbable braided polyester sutures (Ticron or Ethibond) with tapered needles for Pulvertaft weaves and pulley reconstructions; 5-0 and 6-0 polypropylene sutures for peripheral epitenon running coaptations.

Examination Under Anesthesia (EUA)

Once regional anesthesia or general anesthesia is induced and muscle relaxation is established, a structured EUA must be executed before sterile limb preparation:

• Passive Joint Mobility Measurement: Assess passive range of motion of the metacarpophalangeal (MCP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints using a sterile goniometer. Passive flexion must achieve at least 90 degrees at the MCP, 100 degrees at the PIP, and 60 degrees at the DIP joint without elastic rebound contracture.
• Passive Tenodesis Test: Passively cycle the wrist from 45 degrees of flexion to 45 degrees of extension. In an intact digit, wrist extension produces automatic, progressive digital flexion (tenodesis cascade). In chronic tendon disruption, the affected finger remains flaccidly extended, confirming continuity loss and establishing baseline resting tension.
• Donor Autograft Screening: Palpate the palmaris longus tendon at the volar wrist crease. If absent, examine the contralateral wrist. Perform manual palpation of the lower extremity anterior-medial to the Achilles tendon to confirm plantaris availability.

4. Patient Positioning & Setup

The patient is positioned in the supine position on a standard operating table equipped with a radiolucent hand table extension. The operative upper extremity is abducted onto the hand table, ensuring full access to the volar forearm, palm, and digit. If plantaris tendon harvest is planned, the ipsilateral lower extremity is prepped and draped simultaneously, with a sandbag positioned beneath the ipsilateral hip to facilitate internal rotation.

• Tourniquet Placement: A calibrated, pneumatic upper-arm tourniquet is applied over two smooth layers of cast padding high on the proximal arm. Following limb elevation and five minutes of gravity drainage or Esmarch exsanguination, the tourniquet is inflated to 250 mmHg (or 100 mmHg above systolic pressure). Tourniquet duration is tracked strictly, with deflation and reperfusion mandated if operative time exceeds 120 minutes.
• Retraction and Positioning Aids: A malleable lead hand retractor or custom digital finger traps are secured to maintain stable digital extension during palmar and digital dissection corridors.
• Pressure Point Protection: Padding is placed beneath the contralateral elbow to protect the ulnar nerve in the cubital tunnel. The heels, sacrum, and contralateral lower extremity are cushioned with viscoelastic pads.

Safety Check

• Confirm sterile draping allows uninhibited visual exposure from the fingertips to the mid-forearm (or proximal calf if harvesting plantaris).
• Verify that the mini C-arm fluoroscopy unit can transition into the surgical field without contamination, establishing unobstructed lateral and anteroposterior views of the distal phalanx base.
• Execute the surgical safety timeout, verifying patient identity, surgical consent, operative digit, donor harvest site, and presence of all required implants and specialty strippers.

5. Approach

Secondary flexor reconstruction necessitates expansive exposure to clear scarred synovial tissues, inspect the annular pulleys, and access proximal motor tendons. Surgical exposure must protect the digital neurovascular bundles and preserve overlying subcutaneous vascularity.

Surgical Approaches and Exposures

• Extended Volar Bruner Zig-Zag Incision: The standard exposure for digital flexor reconstruction. Angular zig-zag incisions are mapped with the apex of each flap positioned at the lateral end of the digital flexion creases (distal, middle, and proximal digital creases). The oblique limbs are incised at 45-degree to 60-degree angles across the phalangeal segments, preventing longitudinal scar contractures. Flaps are elevated full-thickness deep to the subcutaneous fat, exposing the underlying flexor sheath while protecting neurovascular bundles within the lateral flap bases.
• Midlateral Incision: An alternative approach particularly advantageous in cases with preexisting volar cicatricial skin contractures. The incision is placed along the coronal neutral line of the digit, connecting the dorsal endpoints of the digital flexion creases. Dissection is carried directly down to the lateral border of the phalanges, dorsal to the proper digital neurovascular bundle. Cleland’s ligaments are incised, allowing the neurovascular bundle to be retracted anteriorly within the volar skin envelope, directly exposing the lateral aspect of the flexor sheath and annular pulleys.
• Palmar & Forearm Counter-Incisions: A curvilinear palmar incision along the thenar crease or mid-palmar crease exposes the lumbrical muscles, carpal canal inlet, and the distal FDP/FDS bifurcations. In the forearm, a longitudinal volar incision centered over the interval between the flexor carpi radialis (FCR) and palmaris longus (or developing the Henry interval) exposes the deep flexor digitorum profundus muscle bellies and establishes the proximal anastomosis corridor.

Internervous Planes and Retraction Corridors

• Digital Canal Interval: Within the digit, there is no true internervous muscular plane. Dissection is contained strictly within the fibro-osseous tunnel, which is bounded bilaterally by the proper digital neurovascular bundles lying beneath Grayson’s ligaments (volar to the bundles) and Cleland’s ligaments (dorsal to the bundles). Retraction must be gentle, utilizing moist elastic vessel loops without focal crush injury.
• Volar Forearm Interval: The proximal dissection exploits the intermuscular plane between the flexor carpi radialis (innervated by the median nerve) and the brachioradialis (innervated by the radial nerve). Deep to this plane, the flexor pollicis longus and flexor digitorum profundus muscle bellies are accessed. The anterior interosseous nerve (AIN) courses along the volar surface of the FDP, innervating the radial half of the muscle (index and middle fingers), while the ulnar nerve innervates the ulnar half (ring and small fingers).

Neurovascular Danger Zones

• Proper Digital Neurovascular Bundles: Traverse immediately adjacent to the flexor sheath at the level of the PIP joint. Dense scar tissue frequently tethers the digital nerve directly to the scarred flexor sheath; dissection must proceed from uninjured proximal and distal tissue planes toward the scarred zone using micro-tenotomy scissors under optical magnification.
• Recurrent Motor Branch of the Median Nerve: Crosses the distal margin of the transverse carpal ligament into the thenar musculature. When extending incisions through the carpal canal to retrieve retracted tendons, the release must remain strictly on the ulnar border of the median nerve to prevent denervation of the abductor pollicis brevis.
• Deep Motor Branch of the Ulnar Nerve: Courses deep to the hypothenar muscles in Guyon’s canal and crosses the deep palmar space near the carpal origin of the adductor pollicis. Forceful deep retraction or blind instrumentation in the deep palm risks motor paralysis of the intrinsic musculature.
• Palmar Cutaneous Branch of the Median Nerve: Arises 5 to 7 cm proximal to the wrist crease, traversing between the FCR and palmaris longus tendons before piercing the deep fascia. Forearm counter-incisions must remain ulnar to the FCR tendon or carefully preserve these branches to avoid painful neuroma formation.

6. Technique

The definitive operative technique for flexor tendon reconstruction is presented in sequential, reproducible phases, executing either a single-stage grafting procedure or the benchmark two-stage Hunter reconstruction depending on the structural integrity of the fibro-osseous canal.

Step 1: Exposure and Soft-Tissue Mobilization

Incise the skin along the planned Bruner zig-zag trajectory, elevating full-thickness fasciocutaneous flaps under 3.5x loupe magnification. Mobilize the flaps meticulously, securing their apices with 5-0 nylon retraction sutures. Identify the bilateral digital neurovascular bundles along the entire length of the digit, gently encircling them with moist silicone vessel loops.

Assess digital joint mobility immediately following exposure. If PIP or DIP joint contractures persist despite full surgical exposure, Perform sequential capsular and ligamentous releases. Mobilize the volar plate by dividing the checkrein ligaments at the proximal margins of the PIP joint. If joint contracture continues, perform gentle release of the accessory collateral ligaments until full passive extension is achieved. Do not proceed with tendon grafting in the presence of uncorrected capsular contractures.

Step 2: Flexor Bed Debridement and Pulley Reconstruction

Excise the scarred, degenerated remnants of the FDP and FDS tendons within Zone II, sharply clearing fibrocartilaginous debris from the digital canal. Meticulously Preserve every millimeter of viable native annular pulley tissue, particularly the A2 pulley (over the proximal phalanx) and the A4 pulley (over the middle phalanx). If the native pulleys are intact but stenosed by intraluminal scar, perform careful intraluminal debridement and dilate the pulleys using smooth, graduated urethral sounds or hemostats.

Reconstruct deficient A2 or A4 pulleys if they are ruptured, scarred beyond salvage, or absent. Pulley reconstruction must precede or coincide with spacer rod insertion:

• Extensor Retinaculum Graft (The Gold Standard): Harvest a 10 mm to 12 mm wide strip of extensor retinaculum from the dorsal wrist (over the third or fourth extensor compartment). Position the graft with its smooth, glistening synovial gliding surface facing inward toward the tendon lumen. For A2 reconstruction, pass the retinacular strip subperiosteally around the proximal phalanx deep to the extensor apparatus, or secure it directly to the fibrous lateral phalangeal ridges using 4-0 non-absorbable braided sutures (Ticron or Ethibond) in a horizontal mattress configuration over a trial spacer rod.
• FDS Tendon Slip (Belt-Loop Technique): If an intact FDS tendon slip is available from the discarded flexor apparatus, use a 6 cm to 8 cm longitudinal slip. Pass the slip circumferentially around the phalanx or weave it through residual pulley rim remnants, securing it back onto itself under moderate tension over the trial spacer. The reconstructed pulley must allow effortless passage of the sizing rod without pinching or luminal constriction.

Step 3: Stage I Hunter Rod Insertion and Gliding Tunnel Creation

Select a Dacron-reinforced silicone Hunter tendon spacer rod matching the diameter of the future autograft (typically 3.0 mm for small digits, 4.0 mm for index, middle, and ring digits). Pass the silicone rod through the reconstructed and native annular pulleys (A1 through A4) from proximal to distal using a smooth metallic tendon passer, ensuring no kink or twist occurs within the canal.

Anchor the distal end of the silicone rod securely to the base of the distal phalanx. Prepare a small bony recess at the anatomical FDP footprint on the volar base of the distal phalanx using a 2 mm curette. Secure the distal Dacron core of the rod to the bone using a 3-0 braided polyester suture passed transosseously through the cortex, or anchor it directly into the residual FDP stump insertion with multiple interrupted non-absorbable sutures. Firm distal fixation prevents proximal migration during postoperative passive motion therapy.

Deliver the proximal end of the silicone rod beneath the transverse carpal ligament into the distal forearm counter-incision. Position the proximal rod tip deep to the pronator quadratus within the loose areolar tissue plane of Parona’s space. Crucial Technical Rule: Leave the proximal end of the silicone spacer completely FREE and untethered. Do not anchor the proximal rod. It must be permitted to glide proximally and distally 2 to 3 cm during digital flexion and extension.

Verify passive glide intraoperatively. Manually cycle the digit through ten full passive flexion-extension cycles. The silicone rod must glide effortlessly through the reconstructed pulleys without binding, buckling, or causing pulley dehiscence. Close the incisions meticulously in layers and apply a dorsal blocking splint. Maintain the spacer rod in situ for 2 to 3 months to allow the formation of a glistening, vascularized, mesothelium-lined pseudosheath.

Step 4: Stage II Free Autograft Harvest and Tendon Inset

Stage II is executed 8 to 12 weeks following Stage I, once digital incisions are completely healed, soft tissues are supple, and full passive joint motion is established. Re-exposure is limited strictly to small counter-incisions at the distal phalanx and the distal forearm, leaving the newly formed digital pseudosheath pristine and untouched.

• Autograft Harvest (Palmaris Longus): Make a 1.5 cm transverse incision at the distal wrist flexion crease directly over the palmaris longus (PL) tendon. Place a second small transverse incision at the junction of the proximal and middle thirds of the volar forearm. Elevate the tendon, transect it at the wrist, and thread it through a Brand tendon stripper. Advance the stripper proximally while maintaining steady distal counter-traction, dividing the tendon at its proximal myotendinous junction to yield a 12 cm to 15 cm graft. Keep the graft moist in saline-soaked gauze.
• Alternative Harvest (Plantaris Tendon): If the PL is absent, make a 2 cm longitudinal incision anterior-medial to the Achilles tendon insertion at the calcaneus. Identify the plantaris tendon, transect it distally, and advance a slotted Brand stripper proximally toward the popliteal fossa with the knee maintained in full extension and the ankle in plantarflexion. This yields a strong, slender graft measuring up to 30 cm to 35 cm in length.
• Graft Inset into Pseudosheath: Expose the distal phalanx fixation and the proximal forearm end of the silicone rod. Detach the distal rod from the distal phalanx. Secure the distal end of the harvested autograft to the proximal end of the silicone rod in the forearm using a 2-0 braided traction suture. Gently draw the silicone rod distally through the mature pseudosheath, pulling the autograft smoothly through the digital canal. Meticulously verify that the graft does not twist along its longitudinal axis.
• Distal Insertion Fixation (Transosseous Pull-Out Suture Technique): Decorticate a small 3 mm by 5 mm cortical trough at the base of the distal phalanx using a high-speed micro-burr down to bleeding cancellous bone. Weave a 3-0 polypropylene suture into the distal 1.5 cm of the autograft using a modified Bunnell or Krackow stitch. Pass the two straight Keith needles through parallel drill holes exiting through the dorsal nail plate, tying the suture firmly over a padded, sterile plastic button.
• Alternative Distal Insertion Fixation (Micro Suture Anchor Technique): Decorticate the anatomical FDP footprint. Drive a 1.5 mm titanium or PEEK suture anchor into the cancellous base of the distal phalanx at a 45-degree angle. Weave the high-strength sutures through the graft end in a Krackow pattern, tying down the knot securely to seat the graft directly against cancellous bone.
• Proximal Motor Anastomosis (Four-Pass Pulvertaft Weave): In the distal forearm, identify and mobilize the recipient FDP motor unit. Perform a classic Pulvertaft weave by interweaving the free graft through perpendicular slits created in the recipient tendon using a #11 scalpel blade. A minimum of four passes is mandatory. Secure each pass with interrupted 3-0 braided polyester sutures (Ticron or Ethibond), trimming and burying the tendon tails cleanly.

Critical Move

Digital Cascade Tensioning and Dynamic Tenodesis Verification: Tensioning the proximal Pulvertaft weave is the irreversible step that dictates functional outcome. With the wrist maintained in 20 to 30 degrees of extension, the tension across the Pulvertaft weave must be calibrated so that the reconstructed digit lies in approximately 5 to 10 degrees greater flexion than the normal physiological cascade relative to adjacent digits. This deliberate hyperflexion accommodates post-reconstruction viscoelastic creep and donor muscle elongation.

Immediately perform intraoperative dynamic tenodesis testing before placing final locking sutures:

• Wrist Extension Maneuver: Passively extend the wrist to 45 degrees. The reconstructed finger must smoothly flex into a tight, harmonious fist with the pulp touching or approaching within 5 mm of the distal palmar crease.
• Wrist Flexion Maneuver: Passively flex the wrist to 45 degrees. The reconstructed finger must drop into full, uninhibited extension without residual PIP or DIP flexion contracture.
• Tension Adjustment: If the digit fails to fully extend during wrist flexion, the graft is overtensioned; the provisional sutures must be removed and the weave relaxed by 2 to 3 mm. If the digit fails to flex into the cascade during wrist extension, the graft is undertensioned and will result in permanent active flexion lag. Once ideal tension is confirmed, lock the weave with final mattress sutures.

7. Pearls and Pitfalls

Mastery of flexor tendon reconstruction requires subtle technical nuances to minimize adhesion formation, prevent bowstringing, and guarantee durable tendon healing.

Pearls

• Sizing Rod Trialing: Always pass a flexible sizing trial rod through reconstructed pulleys prior to opening the definitive sterile silicone implant. The reconstructed pulley must encircle the rod loosely enough to allow free axial glide with zero friction, yet tightly enough to prevent palmar displacement greater than 2 mm.
• Beveling Pulley Edges: Use fine micro-tenotomy scissors to sharply bevel the proximal and distal luminal margins of reconstructed pulleys. Chamfering these edges prevents the tendon graft or suture coaptation from catching abruptly during active excursion.
• Preservation of Parona’s Space: In Stage I, deliver the proximal tip of the silicone spacer deep to the pronator quadratus. This protects the median nerve from mechanical friction and ensures the rod moves freely within areolar tissues during digital motion.
• Knee Positioning During Plantaris Harvest: Maintain the patient’s knee in complete extension and the ankle in full plantarflexion while advancing the Brand tendon stripper. This relaxes gastrocnemius muscle tension, preventing premature shearing or transection of the plantaris graft before reaching its proximal origin.
• Four-Pass Pulvertaft Integrity: Ensure a minimum of four perpendicular weaves are completed at the proximal motor anastomosis. Biomechanical testing confirms four perpendicular passes achieve greater than 85% of native tendon tensile strength, permitting early protected active motion.

Pitfalls

• Overtensioning the Reconstructed Graft: Setting the graft under excessive tension precipitates digital flexion contracture and triggers the quadrigia effect, where restricted excursion of the reconstructed profundus tendon limits active flexion of adjacent normal fingers sharing the common profundus muscle belly.
• Neglecting A2/A4 Pulley Incompetence: Failing to reconstruct deficient A2 or A4 pulleys results in severe flexor tendon bowstringing. Bowstringing increases the moment arm of the tendon, requiring substantially greater muscle excursion to produce angular joint motion and resulting in permanent active flexion lag.
• Lumbrical Plus Deformity: Occurs when the tendon graft is too long or distal fixation is set distal to the lumbrical origin without releasing a scarred lumbrical muscle. Attempted active digital flexion pulls through the lumbrical tendon, paradoxically extending the PIP joint. Rescue maneuver: sharp surgical transection of the radial lumbrical tendon insertion at the MCP level.
• Proximal Anchoring of the Stage I Rod: Suturing or anchoring the proximal end of the silicone spacer rod in the forearm prevents passive gliding, causes severe rod buckling within the digit, and destroys the nascent pseudosheath.
• Operating in a Stiff Digit: Attempting tendon reconstruction before eradicating passive joint contractures uniformly fails. A tendon graft can never exceed the passive range of motion of the digital joints.

8. Postoperative Care

Rehabilitation following flexor tendon reconstruction must balance early controlled mobilization to prevent peritendinous adhesion formation with absolute mechanical protection of healing coaptation sites.

Immediate Care

Immediately following wound closure and dressing application in the operating room, a rigid custom dorsal blocking splint is applied:

• Splint Configuration: The dorsal blocking splint positions the wrist in 20 to 30 degrees of flexion, the MCP joints in 50 to 60 degrees of flexion, and allows the interphalangeal (IP) joints to rest in complete extension (0 degrees). A static volar block or finger straps are avoided to prevent PIP joint flexion contractures.
• Limb Elevation & Pain Control: Strict elevation of the extremity above heart level is enforced to mitigate swelling. Multimodal non-opioid analgesia is initiated, avoiding excessive NSAID use during early bone-tendon healing.
• Button & Skin Care: If a dorsal pull-out button was utilized, inspect the dorsal nail plate daily. Ensure felt bolster padding prevents localized pressure necrosis of the germinal matrix.

Rehabilitation Protocol

A structured, four-phase hand therapy protocol is directed by a certified hand therapist, progressing from protected passive motion to unrestricted resistive loading:

9. Outcome

Clinical outcomes following secondary flexor tendon reconstruction are rigorously evaluated using validated hand surgery scoring systems that quantify Total Active Motion (TAM) and distance from the fingertip to the distal palmar crease.

The Strickland Classification and Buck-Gramcko Scoring System represent the worldwide benchmarks for reporting functional results in flexor tendon surgery. The modified Strickland system evaluates active range of motion across the PIP and DIP joints relative to normal functional arc (175 degrees):

Strickland Score (%) = [(Active PIP Flexion + Active DIP Flexion) – (PIP Extension Deficit + DIP Extension Deficit)] / 175 degrees x 100

Longitudinal published series document good-to-excellent functional recovery in 70% to 85% of digits undergoing staged Hunter reconstruction in Boyes Grade II and III flexor beds. Conversely, in severely mangled extremities characterized by combined neurovascular injury, multiple digital trauma, or extensive burn scar contracture (Boyes Grade IV and V), the rate of good-to-excellent outcomes drops to 50% to 60%, with higher rates of secondary tenolysis and permanent flexion deficit.

10. Complications

Secondary flexor tendon reconstruction is technically unforgiving, carrying inherent risks of adhesion development, graft disruption, biomechanical imbalances, and joint stiffness. Surgeons must actively monitor for early warning signs of failure and implement prompt revision strategies.

11. Evidence-Based Synthesis

Modern flexor tendon reconstruction protocols are underpinned by seminal longitudinal cohorts and contemporary comparative trials defining functional outcomes, anti-adhesion biological adjuncts, and optimal rehabilitation regimens.

12. References

• Shaw AV, Holmes DG, Rodrigues JN et al. Outcome measurement in adult flexor tendon injury: A systematic review. J Plast Reconstr Aesthet Surg. 2022;75(3):1042-1051. doi:10.1016/j.bjps.2021.08.033 [Level I: Systematic Review / Meta-Analysis]
• Brady C, Lee A, Gardiner M et al. The outcomes of zone 1 flexor digitorum profundus tendon injury: A systematic review and meta-analysis. J Plast Reconstr Aesthet Surg. 2022;75(4):1380-1390. doi:10.1016/j.bjps.2021.11.026 [Level I: Systematic Review / Meta-Analysis]
• Lee YJ, Ryoo HJ, Shim HS. Prevention of postoperative adhesions after flexor tendon repair with acellular dermal matrix in Zones III, IV, and V of the hand: A randomized controlled (CONSORT-compliant) trial. Medicine (Baltimore). 2022;101(3):e28630. doi:10.1097/MD.0000000000028630 [Level I: Randomized Controlled Trial]
• Hunter JM, Salisbury RE. Flexor-Tendon Reconstruction in Severely Damaged Hands. A new technique using a silicone-dacron reinforced gliding artificial tendon. J Bone Joint Surg Am. 1971;53(5):829-858. doi:10.2106/00004623-197153050-00001 [Level IV: Seminal Landmark Cohort]
• Wehbé MA, Hunter JM, Schneider LH, Goodwyn BL. Two-stage flexor-tendon reconstruction. Ten-year experience. J Bone Joint Surg Am. 1986;68(5):752-763. doi:10.2106/00004623-198668050-00019 [Level IV: Longitudinal Landmark Series]
• Amadio PC, Wood MB, Cooney WP, Bogard SD. Staged flexor tendon reconstruction in the fingers and hand. J Hand Surg Am. 1988;13(4):559-562. doi:10.1016/s0363-5023(88)80095-9 [Level IV: Clinical Cohort / Prognostic Study]
• Al-Qattan MM. Two-stage reconstruction with the modified Paneva-Holevich technique. Hand Clin. 2013;29(2):235-245. doi:10.1016/j.hcl.2013.02.011 [Level IV: Clinical Cohort / Technique Analysis]
• Draeger RW, Bindra R. Flexor Tendon Reconstruction. Hand Clin. 2023;39(2):207-217. doi:10.1016/j.hcl.2022.08.020 [Level V: Expert Comprehensive Review]

13. Master Class Pro-Tip

The most catastrophic yet preventable error in flexor tendon reconstruction is tensioning the graft to match the anatomical cascade under passive static rest without performing active tenodesis validation. Always calibrate graft tension with the wrist positioned in exactly 20 to 30 degrees of extension, setting the reconstructed digit in 5 to 10 degrees greater flexion than the adjacent fingers to anticipate inevitable viscoelastic elongation. Prior to locking the Pulvertaft weave, fully flex the wrist to 45 degrees: the reconstructed finger must passively drop into completely unobstructed, full extension. If even 5 degrees of residual flexion resistance persists at the PIP joint during wrist flexion, the graft is overtensioned and will irrevocably induce quadrigia stiffness. Conversely, if extending the wrist fails to pull the fingertip into the palmar cascade, the graft is undertensioned and will never actively flex. Meticulous dynamic tenodesis testing eliminates the narrow boundary between catastrophic joint contracture and permanent flexor lag.

Master Class Surgical Pearl: Flexor Tendon Reconstruction